The present invention relates to ultrasound transmitters. In particular, a transmitter is operable for both pulsed wave and continuous wave modes.
Ultrasound transmitters include waveform generators for generating different types of waveforms. Pulsed waveforms are relatively high voltage waveforms, such as 20-200 volt peak amplitude, of short duration, such as one to three cycles. Unipolar or bipolar pulsed waves may be generated using one or more transistors. The transistors are switched on and off, connecting a high voltage sources (±) or ground to an output. For continuous wave operation, a multi-cycle waveform, such as ten or more cycles (e.g., generating MHz waveforms for minutes), with relatively lower voltage, such as 2.5 to 12 volts, is generated. Transistors for operating at high voltages inefficiently operate at lower voltages.
Many ultrasound systems use separate circuits for generating pulsed and continuous waves. Separate circuits are provided in different application specific integrated circuits, chips or even boards. The low voltage circuitry for continuous wave operation is not subjected to the high voltages of the pulsed waves.
Where space, power availability or heat dissipation restrictions exist, sacrifices in the types of waves transmitted may result. For example, transmitters integrated into a multi-dimensional transducer array housing have been developed to provide pulsed waveform generation. However, efficient continuous wave operation is still desired even for real-time three-dimensional imaging provided by multi-dimensional arrays with integrated transmitters.